1. Field of the Invention
The present invention relates to a magnetic recording medium having excellent balanced dynamic ranges in long wevelength and in short wavelength.
2. Description of the Prior Art
Recently, a magnetic recording medium has been remarkably developed. The practical developments for simplification in a compact cassette and a microcassette and high densityfication in a video tape are significant.
In view of recording having high fidelity in reproduction of the original signal, distortion of said developed products in a large input has not been satisfactory because of the consideration of simplification and miniaturization.
The inventors have been studied to improve quality of the magnetic recording and have succeeded in the present invention.
Referring to "Tape Recorder" published by Nippon Broadcast Publication Associate on Mar. 20, 1969 written by Miharu Abe, the magnetic recording problem will be illustrated.
In the normal magnetic recording, increase of an input level substantially corresponds to increase of an output. In a case of bias recording, a noise in reproduction at non-signal input (hereinafter referring to as bias noise) is depending upon a medium whereby a ratio of signal to noise (S/N ratio) seems to be increased. In low frequency, ghost signals having magnified frequencies (hereinafter referring to harmonic waves) are given beside the original signal input. The output of the harmonic waves also increase depending upon the increase of the input level at higher ratio whereby the waveform of the reproduced signal is distorted from sine wave. In quantitative measurement of distortion, it is usual to consider the third harmonic wave having triple frequency to the original signal among these harmonic waves and to consider as an allowable distortion, an input level of the output of third harmonic wave for 3% of the output of the original signal "input in 3% distortion".
In high frequency recording, the reproduced signal can not follow to the increase of the input level. Even though the input level increases the reproduction output is not further improved to be saturation as the phenomenon. The input level at the saturation is referred to as "saturated input level" and the output is referred to as "saturated output".
The magnetic recording medium has critical wavelength for recording depending upon the material thereof. In analogue recording, the critical wavelength is preferably short wavelength. That is, it is possible to record for high frequency region. In digital recording, it is preferable to have broad frequency region in view of discretional consideration for signal regions in the recording.